$ { {3} \times \left[\begin{array}{rrr}{2} & {-1} & {3} \\ {1} & {2} & {3}\end{array}\right] = {?} } $
Explanation: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{3}\times{2} & {3}\times{-1} & {3}\times{3} \\ {3}\times{1} & {3}\times{2} & {3}\times{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{6} & {-3} & {9} \\ {3} & {6} & {9}\end{array}\right]}$